A particular problem with prior art encapsulation matrices has been their inability to hold more than about 10% by weight of an encapsulate or dispersed phase, such as an essential oil. Accordingly, a principal object of the present invention is to provide an improved matrix composition adapted for extrusion and further having an improved capacity to contain in a stable manner a normally liquid dispersed phase, such as an organoleptic material, e.g., lemon oil, orange oil, or the like.
This improvement arose out of work originally done by Beck as described in U.S. Pat. No. 3,704,137 dated Nov. 28, 1972. This patent describes certain relatively stable particulate essential oil-containing compositions and a process for making the solid particulate material. The procedural steps described by Beck can be used in preparing the novel encapsulates of the present invention. We have found that the load carrying capacity of the Beck material is below about 10% by weight. It has been found that increased loading capacity can be achieved by formulating a matrix composition to contain (a) maltodextrin, a starch hydrolysate, and (b) a modified starch which is a derivative of waxy maize. The composition is characterized by high load capacity for an active ingredient, and handleability according to the Beck procedure, supra, at reasonable pressures and temperatures. A similar procedure is disclosed in Swisher U.S. Pat. No. 3,041,180.
Currently, modified starches are used in the production of spray dried flavors, but they are not used commercially as an ingredient in extrusion encapsulation process formulations. These encapsulation processes are basically different. In encapsulating by spray drying, flavorant and emulsifier are added directly to the encapsulation matrix consisting of water, maltodextrin, gum arabic, etc. Water is then removed by spray drying. The product is porous and not as stable as that produced by extrusion technology. In the latter case, water is removed before flavor is added and locked in as in U.S. Pat. No. 3,704,137, supra. Extrusion products have superior shelf stability. However, until the present invention, active ingredient loadings available in extrusion were much lower (9-10%) than the 15 to 25% levels typical of spray dried products. According to the present invention, the advantages of extrusion encapsulation such as stability can be realized and loadings of up to 20-35 or 40% achieved. Still further, certain of the prior art encapsulation procedures require substantial extrusion pressures and equipment capable of handling such pressures. These pressures are commonly above 1000 psi, e.g., 3000 to 4000 psi. The present invention allows extrusion to occur at pressures below 150 psig. and generally below 100 psig.
Various methods of producing maltodextrins are known. Maltodextrins are identified by Chemical Abstracts Registry No. 9050-36-6. Reference may be had to U.S. Pat. No. 3,974,033 to Harjes et al dated Aug. 10, 1976 and to the prior art discussed therein. The maltodextrins useful herein have a low DE (dextrose equivalent), i.e., in the range of 3 to 40. Generally, they are made by first liquefying native starch with an acid or an enzyme to a DE less than about 15, followed by enzymatic conversion, e.g., with bacterial alpha-amylase (See U.S. Pat. No. 3,849,194 and Re. 30,880). As pointed out in U.S. Pat. No. 3,974,033, maltodextrins are first prepared in syrup form and then spray dried to a moisture content of 3-5% by weight. These prior art maltodextrin materials and those prepared from oxidized starch as described in U.S. Pat. No. 3,974,033 are useful herein.
The second principal ingredient of the improved matrix compositions hereof is a derivative of waxy maize identified as hydrogen octenylbutanedioate amylodextrin. It has a Chemical Abstracts Registry Number 61932-62-5. This material is commercially available from National Starch and Chemical Corp. as "Capsul". "Capsul" has been used as an encapsulating agent in spray drying techniques. (See "Modified Starch Encapsulating Agents Offer Superior Emulsification, Film Forming, and Low Surface Oil" by King et al, Food Product Development, Volume 10, No. 10, pages 54, 56, 57, December, 1976; and Sair et al U.S. Pat. No. 4,232,047, particularly Example 9 in Column 14, describing extrusion of a mixture of "Capsul brand dextrin" and beef extract in a Brabender extruder). In using these materials as extrusion encapsulating matrices, the emulsions become too viscous and extrusion pressures in the range of from 800 to 4000+ psi are rquired. The cost limitations imposed by equipment able to generate and withstand extrusion pressures for these materials is prohibitive. Again, as previously indicated, for this and other reasons, the modified starches are not used today commercially as an ingredient in extrusion encapsulation process formulations. According to the present invention, the maximum extrusion pressure is below 150 psi, and usually below 100 psi. The two principal ingredients, when blended together with water and heated, preferably although not essentially under vacuum, to remove 85% or more of the water, form a composition which is normally solid and is soluble in water at ordinary temperatures.
As indicated above, the combination of maltodextrin and "Capsul" enables high loading of active ingredients and extrusion at pressures below 150 psi. None of the prior art of which we are aware suggests or discloses this combination of starch derivatives as a matrix composition for extrusion encapsulating active ingredients.
Another ingredient which is desirably, although not essentially present is an emulsifier. This material is desirably edible, although where insecticides or maturation inhibitors are involved the emulsifying agent may be inedible by humans. In general, the emulsifiers are present in amounts from 0.25 to 5% by weight, and usually from 1% to 3%. Higher levels of emulsifier may be used, but appear not to be beneficial, and at the same time are not harmful. Specific examples of emulsifying agents useful herein include diacetyl tartaric acid ester of a mono-diglyceride of C.sub.8 -C.sub.18 fatty acids, e.g., palmitic stearic or oleic acids, ethoxylated mono-diglycerides, mono-diglyceride sodium sulfoacetate, monostearin sodium sulfoacetate, polymeric alkylaryl polyether alcohol, polyethylene glycol oleates or stearates, sodium lauryl sulfate, vegetable oils, glyceryl monooleate, glyceryl monostearate, sorbitan monostearate, acetylated monoglycerides, sodium stearoyl-2-lactylate, citrus stereoptene, lecithin, gum arabic, gum acacia, locust bean gum, guar gum, tragacanth gum, pectin, pectin albedo, agar agar, algin, hydrogenated animal fat, etc. Also useful as emulsifiers are the sulfonate salts, e.g., sodium lauryl sulfonate, sodium petroleum sulfonate, sodium napthalene sulfonate, etc.